A conventional tubular latch as shown in FIG. 8 includes a latch L resiliently held in a housing S fixed in a tubular hole formed in a door R and operatively retracted for opening the door by biasing a door handle H (direction R1) whereby a cam C as rotated (in direction R2) by the handle H will pull a driving plate D secured with the latch L to retract the latch L in rearward direction R3 for opening the door.
For biasing the handle H for opening the door, it will require a greater rotating angle A (such as 70 degrees) since a stroke L2 for retracting the latch L in direction R3 for opening the door equals to an arc length of the rotated cam C of the handle H and the retraction of the latch L should be directly actuated by rotating the cam C and handle H, thereby causing an inconvenient door opening operation by baising the handle with a greater rotating angle, especially inconvenient for the door opening by a passer-by whose two hands carrying a heavy goods or by a diabled person.